Pulse duration coded electronic lock and key system



July 16, 1968 R. A. HEDIN ETAL 3,392,559

PULSE DURATION CODED ELECTRONIC LOCK AND KEY SYSTEM Filed oct. 24, 1965 5.1% il ROBE/2T ,ZI.. HELD/N ALF/E120 I. Bm. zNo

By 771m United States Patent O 3,392,559 PULSE DURATION CODED ELECTRONIC LOCK AND KEY SYSTEM Robert A. Hedin, 1700 Cumbre Drive, San Pedro, Calif.

90732, and Alfiero F. Balzano, 7814 Foothill Blvd.,

Sunland, Calif. 91040 Filed Oct. 24, 1965, Ser. No. 504,582 Claims. (Cl. 70-277) ABSTRACT OF THE DISCLOSURE The electronic lock and key system disclosed herein includes a iirst pulse generator for generating a key pulse of a given duration upon being energized and a second pulse generator for generating a lock pulse having a duration at least as long as the key pulse. Means are provided for engaging and receiving a key means and a source of operating po-tential is connected to the key means for energizing both the irstand second pulse generators at the same time Whenever the key means is in engagement with the key engaging means. A gate means is responsive to the synchronous occurrence and termination of the key pulse and the lock pulse so as to generate a control signal which is introduced to an electronic latch means for unlocking the system.

This invention relates to lock apparatus such as may be used for entrance doors, vaults, and the like, and more particularly to an electronic lock and key system employing a pulse-width generator as a key device and a pulse decoding circuit as a lock device, each of which may be selectively encoded to provide various combinations corresponding to levels of access.

There have been proposed, heretofore, various schemes for constructing electronic permutation locks. Typically, these prior schemes have employed frequency responsive lock circuits whi-ch are designed to coact with a key device capable of establishing a particular frequency or combination of frequencies in order to unlock the latching mechanism. While such devices haveprovided a number of desirable features, including a large number of available combinations, they have failed to achieve any substantial commercial success due to their excessive cornplexity, large size, high cost land inadequate reliability. Also, they have, for the most part, lacked flexibility with respect to encoding or re-encoding the keying device. The present invention overcomes these shortcomings of prior devices and also provides a number of advantages over devices heretofore intended for generally similarly purposes..

The system of the present invention comprises 4a key device having an extremely small pulse generator contained therein. This key device is adapted to mate with a corresponding lock receptacle in order to obtain an operating potential therefrom and to transmit a unique pulse-duration modulated (PDM) code thereto. The lock receptacle applies the received PDM code to a decoding or logic circuit which is responsive to a given PDM code to activate an electromechanical latch or other electrically actuated lock mechanism. The use of a PDM code makes available an extremely large number of code combinations. Either a one-pulse or a multiple-pulse code may be employed. depending upon the desired range of code permutations.

The lock and key system of the invention provides a number of useful features and advantages unobtainable in prior electric or electronic lock and key systems. For example, the present invention provides the utmost ease in changing the key code, since it is merely necessary to make a simple potentiometer adjustment in both the 3,392,559 Patented July 16, 1968 key and lock. Another advantage of the present invention is that no power is utilized until the key is inserted into the lock. Also, several keys can be made to operate a given lock, but each of these several keys may be made distinctly diiferent so that each will also operate a corresponding one of a plurality of independent locks.

An unusually high degree of security is provided by the system of the present invention since its construction thwarts all presently known techniques employed to compromise the security of lock systems. Inasmuch as the operation of the lock depends upon the generation of certain electrical signals, lock receptacle redundancy may be incorporated into a particular lock installation thereby permitting multiple-station or remote operation.

In a typical installation of the system of the present invention, the key receptacle is located in a conveniently exposed position adjacent the door which is to be locked. A cable having a plurality of labeled conductors extends from the key receptacle to the lock decoding and logic circuits. This arrangement permits these circuits to 'be located in a secure place which is inaccessible to unauthorized persons. However, the construction of the invention, as will be seen hereinafter, permits an authorized person to readily change the key code and provide a corresponding key. Other modications are also possible. For eX- ample, many levels of master keys may be provided as in the case of an apartment building wherein all tenants are provided with a key which will unlock the main entrance to the building, but which key will also unlock but a single one of the several apartments within the building. This same key may be further adapted to open a particular door within the given apartment whereas other keys adapted to open this same given apartment would not provide access to the particular door.

Having in mind the defects of prior art electrical lock devices, it is an object of this invention to provide an electronic lock and key system which over-comes the dificulties and disadvantages of such prior devices.

Another object of the present invention is to provide a. novel and improved electronic lock and key system which provides greater security, more flexibility of ap plication, and more compactness in size than similar devices heretofore known in the art.

Still another object of the present invention is to provide a novel and improved electronic lock and key system utilizing pulse-duration modulation in the permutation of the key codes.

Yet another object of the present invention is to provide a novel and improved electronic lock and key system employing ya key device for generating a pulse-duration code and a lock device responsive to said pulse-duration code to permit access to a secure area or to operate a secured electrical device.

iIt is still another object of this invention to provide a novel `and improved electronic lock and key system employing a pulse-duration coding means having great ilexibility in the permutation of the code and which permits redundant oper-ation, and/or the use of a number of levels of master keys and/ or master locks.

Other objects, features and advantages of this invention will in part be obvious -and will in part appear hereinafter.

Many variations wil lbecorne obvious in this invention t-o those versed in the Iart upon consideration of the f following specification and drawings in which:

FIGURE 1 is a block diagram illustrating the components of a typical lock and key system constructed in accordance with the present invention, and having a pair of pulse generators in the key device.

FIGURE 2 is a schematic circuit diagram illustrating one means of implementing the Ibasic system of FIGURE 1, but with single pulse generator in the key device.

Referring now to FIGURE l, there is shown a key device 1 which is adapted to engage with lock receptacle 2 in order to complete a plurality of circuit paths therebetween. Preferably, key device 1 comprises an integrated solid-state circuit contained within a durable electrically insulative housing of approximately the volume as a conventional key for a mechanical lock. Electrical connections to the circuit within the key are made available -at the exposed surface of the key housing by any suitable and well-known contact means. As is well-known to those versed in the art, electronic circuit devices may be tremendously reduced in size by means of the so-called integrated circuit fabrication technique. Also, such integrated circuits are extremely rugged and immune to mechanical shocks. Inasmuch as a typical key circuit of the present invention employs but tive electronic circuit elements, of the type which may readily be fabricated by the above-mentioned technique, it is preferred that integrated circuits be employed in the construction of the key device 1.

Key device 1 contains pulse generator 3 and pulse generator 4. A plurality of contacts 5-10 disposed at the exterior surface of key device 1 lmate with corresponding terminals on lock receptacle 2 in order to complete the necessary circuit paths between the lock and the key.

Power supply 12 provides operating potential to the key device 1 via contact 5 and line 13. Operating potential is also supplied to the lock decoding circuit via contact 6 .and line 14 whenever the key is inserted in the lock. The circuits are referenced to ground 15 via contact 10. Normally no power is used when the key is removed from the lock. When the key device 1 is inserted into lock receptacle 2, the operating potential on line 16 is instantaneously applied to generators 3 and 4, and to certain components of the lock circuit. In response to the application of operating potential, pulse generator 3 will generate a pulse of a given time duration (viz. pulse width) which is sent via `contact 7 and line 17 to silicon controlled rectifier (SCR) 18. The pulse on line 17 will cause SCR 18 to ire for the purpose of preventing the lock from responding to other than the first pulse received from the key. That is, this will prevent the lock from being swept with a variable width pulse. Conduction of SCR 18 will generate a negative-going voltage which is applied to diiierentiator 19. The differentiated pulse appearing on line 21 is applied to one input of AND gate 22.

The application of operating potential via key contact 6 and line 14 will also energize pulse generator 23 in the lock circuit. The output pulse from generator 23 will cause SCR 24 to re. Conduction of SCR 24 will trigger one-shot multivibrator 25 and thereby provide an output pulse on line 26 to a second input to AND gate 22. This arrangement permits only one pulse to appear at the second input of the AND gate 22 each time the key 1 is inserted into the lock 2. The width of the pulse on line 26 will depend upon the degree of stability and tracking accuracy between pulse generator 3 and pulse generator 23, and it is this coincidence in pulse width which comprises the key code. If both pulse generators 3 Iand 23 operate at the same time in response to the insertion of the key 1, both inputs 21 and 26 to AND gate 22 will be coincident in time and the output 27 will go true (be energized).

Assuming that key device 1 is provided with but a single pulse generator, rather than the two ygenerators 3 and 4 which are shown, then the output 27 may be used directly to energize or trigger an electric latch or other utilization device.

In this connection, it should be understood that the utilization device may comprise either an electro-mechanically actuated latch or lock mechanism, or may comprise any other electrically operated device such as a camera, recorder, weapon system, etc.

In the embodiment shown in FIGURE l, the key device employs two pulse generators, thus providing a greater range of code permutations than is practical 0r feasible with a single PDM code. In addition to the above-described circuit functioning, the output 27 of AND gate 22 simultaneously triggers pulse generator 4 and pulse Vgenerator 28. The output of pulse generator 4 is supplied via contact 9 and line 29 to ditferentiator 31. The diiierentiated pulse appearing on line 32 comprises one input AND gate 33. The output pulse from generator 2S is supplied to one-shot multivibrator 34 from which a pulse of a given width emerges on line 35, comprising a second input to AND gate 33, following its activation by generator 28.

Assuming that the width of the pulse on line 29 coincides with the width of the -pulse on line 35, and also assuming that they are coincident in time, then a true output will be obtained from AND gate 33 on line 36. It should be understood, of course, that this condition requires that both the first and second pulses generated by the key device 1 are identical with those generated in the lock. The presence of a true output on line 36 will lire SCR 37 and thereby energize the electric latch 38, via line 39.

If it is desired to have several keys open the same lock, then the width of the pulse obtained from either one, or both, of the one-shot multivibrators 25 and/or 34 can be increased until it encompasses the pulse width obtained from all of the desired keys.

In connection with the above description of the block diagram illustrating one embodiment of the invention, it should be understood that circuit details of the individual blocks have been omitted since any one of several suitable components, capable of performing the intended function of the blocks shown and well known in the art may be employed. Also, it should be understood that certain obvious variations and/or substitutions in the above-described circuit components may be made. For example, the silicon controlled rectiiiers 18, 24, and 37 may be replaced with any suitable bistable or two-state device capable of performing a similar function.

By way of example, there is shown in FIGURE 2 a schematic circuit diagram of one means of implementing the above-described system. The embodiment of FIG- URE 2 employs but a single PCM pulse generator in the key, but the manner in which the system may -be extended to incorporate multiple pulse codes will become readily apparent to those skilled in the art. The key 41 contains unijunction transistor 42 which is connected across the power supply via resistors 43 and 44, and contacts 45 and 46. The positive terminal of the ypower supply (not shown) connects to line 47 which leads to key contact 45. The negative or return terminal of the power supply connects to line 48 which leads to key contact 46. The emitter of transistor 42 is connected to the midpoint of the series network comprising potentiometer 49 and capacitor 51. The return power supply connection to the lock circuits is provided via contact 52. The output pulse from the key 41 is sent to the lock circuit via contact 53, and is applied to the gate electrode of silicon con trolled rectifier 54. The anode of SCR 54 is connected to the positive power supply line 55 via resistor 56; the cathode of SCR 54 is returned to the negative power supply line 48. The diiferentiator comprises resistor 57 and capacitor 58.

The differentiated pulse on line 59 is supplied to one input of the AND gate comprising transistors 61 and 62, and resistors 63-65. The pulse generator contained within the lock circuit comprises unijunction transistor 66, resistors 67-68, capacitor 69, and potentiometer 71. As can be seen, this pulse generator has the same configuration as the pulse generator in the key 41.

When the key 41 is inserted into the lock, the voltage from the power supply terminal 47 is routed to both the lock and the key. A charge is then built up on capacitors 51 and 69 through charging resistances 43, 49, and 67,

71 respectively. Potentiometers 49 and 71 adjust the charging time, and hence can be used to vary the pulse Width, which is to say varies the key code. When the firing potentials of unijunction transistors 42 and 66, respectively, discharge through corresponding ones of resistors 44 and y68, the pulses thus generated cause corresponding ones of SCRs -54 and 72 to fire and additional pulses from the key 41 will have no effect on the lock. The width of the output pulse supplied to the gate electrode of SCR 72, may be varied by suitably adjusting potentiometer 71. The anode of SCR 72 is connected to the positive power supply line 55 via series resistor 73.

The one-shot multivibrator which is triggered by SCR 72, comprises cross-coupled transistors 74 and 75. The input pulse is supplied to the base of transistor 74 via coupling capacitor 76. The collector of transistor 75 is coupled back to the input at the -base of transistor 74 via capacitor 77. The output of transistor 74 is coupled to the base of transistor 75 via resistor 78. Bias and operating potentials are supplied to the multivibrator via resistors 81-83.

The second input to the AND gates 61-62 is obtained from the collector of transistor 75 via resistor 64. When the output of the AND gate is true, a pulse will appear at the collector of transistor 62 which in turn triggers the gate electrode of SCR 79.

Coil 84 comprises the actuator coil of the electric latch or other utilization device, and is in series with the anode of SCR 74. Thus, when SCR 79 is fired, coil 84 will remain energized until the power supply voltage is removed from line 55 by withdrawing the key 41 from the lock.

It will be obvious from the foregoing that the apparatus of FIGURE 2 can be extended to include the double-pulse concept of FIGURE 1 by the appropriate addition of the above-described sub-circuits.

While the invention has been illustrated and described in terms of a particular embodiment, it is not intended to be limited to the details shown, since various modifications, omissions, and structural changes may be made without departing in any way from the actual scope of the invention. It is, therefore, intended that the invention be limited only by the following claims.

We claim:

1. An electronic lock and key system comprising:

a first pulse generator for generating a key pulse of a given duration upon bein-g energized;

key means carrying said pulse generator;

a second pulhe generator for generating a lock pulse having a duration at least as long as said key pulse;

means for receiving said key means;

a source of operating potential connected to said key engaging means for energizing both said first and second pulse generators at the same time whenever said key means is in engagement with Said key engaging means;

gate means substantially responsive only to the synchronous occurrence and termination of said key pulse and said lock pulse to generate a control signal; and

electric latch means connected to said gate means and responsive to said control signal to unlock said system.

2. An electronic lock and key system as defined in claim 1 wherein said gate means comprises:

an AND gate having first and Second inputs land an output, said first input being connected to said rst pulse generator via a pulse trailing edge detector, .and said second input being connected to said second pulse generator via a tolerance generator operable in response to the trailing edge of said lock pulse, and said output being connected to said electric latch means.

3. An electronic lock and key system comprising:

first and second key pulse generators;

a key member carrying said first and second key pulse generators;

a lock receptacle for engaging said key member;

la source of operating potential connected to lock receptacle for energizing said first key pulse generator when said key member is in engagement with said lock receptacle and thereby produce a first key pulse therefrom;

first and second lock pulse generators connected to said lock receptacle, said rst lock pulse generator being responsive to the engagement of said key member Vand said lock receptacle for generating a first lock pulse, and said second pulse generator being responsive to said first key pulse to generate a second lock pulse;

a coincidence circuit responsive to the synchronous generation of said first and second lock pulses to generate a first control pulse;

means for supplying said first control pulse to said second key pulse generator and thereby produce a second key pulse therefrom;

gate means responsive to the synchronous generation of said second key pulse and said second lock pulse to generate a second control pulse; and

electric latch means connected to said gate means and responsive to said Second control pulse to unlock said system.

4. An electronic lock and key system comprising:

key pulse generating means for generating a pulseduration digital coded pulse in response to an operating potential applied thereto;

lock pulse generating means for generating a lock pulse havin-g a pulse duration at least equal to said coded pulse, in response to an operating potential applied thereto;

pulse comparison means for generating a control pulse only in response to synchronism between the leading and trailing edges of said coded pulse and said lock pulse;

a source of operating potential;

means for selectively connecting said source of operating potential to said key pulse generating means and said lock pulse generating means; and

means connected to said comparison means and responsive to said control pulse.

5. An electronic lock and key system comprising:

a rst pulse generator for generating a key pulse of a given duration upon being energized;

key means carrying said pulse generator;

a second pulse generator for generating a lock pulse having a duration at least as long as said key pulse;

means for receiving said key means;

a source of operating potential connected to said key engaging means for energizing said first and second pulse generators whenever said key means is in engagement with said key engaging means;

gate means responsive to the synchronous occurrence of said key pulse and said lock pulse to generate a control signal;

electric latch means connected to said gate means and responsive to said control signal to unlock said system;

said rst pulse generator comprising:

a u-nijunction transistor;

a first charging resistor connected between one terminal leading to said source of operating potential and one base electrode of said transistor;

a second charging resistor connected between said one base electrode and the emitter of said transistor;

a lcharging capacitor connected between said emitter and the other terminal leading to said source of operating potential; and

a discharging resistor connected between the other base electrode of said transistor and said other terminal.

6. An electronic lock and key system comprising:

a rst pulse generator for generating a key pulse of a given duration upon being energized;

key means carrying said pulse generator;

a second pulse generator for generating a lock pulse having a duration at least as long as said key pulse;

means for receiving said key means;

a source of operating potenti-al connected to said key engaging means for energizing said tirst and second pulse generators whenever said key means is in engagement With said key engaging means;

gate means responsive to the synchronous occurrence of said key pulse and said lock pulse to generate a control signal;

electric latch means connected to said gate means and responsive to said control signal to unlock said system;

key pulse modifying means interposed between said key engaging means and said gate means, said key pulse modifying means comprising:

a bistable conduction means responsive to said key pulse -to generate a step-function pulse; and

a pulse differentiator connected to said bistable conduction means to provide a differentiated pulse to said gate means of a given pulse duration.

7. An electronic lock and key system comprising:

a first pulse generator for generating a key pulse of a given duration upon being energized;

key means carrying said pulse generator;

a second pulse generator for generating a lock pulse having a duration at least as long as said key pulse;

means for receiving said key means;

a source of operating potential connected to said key engaging means for energizing said first and second pulse generators whenever said key means is in engagement with said key engaging means;

gate means responsive to the synchronous occurrence of said key pulse and said lock pulse to generate a control signal;

electric latch means connected to said gate means and responsive to said control signal to unlock said system;

lock pulse modifying means interposed between said key engaging means and said gate means, said lock pulse modifying means comprising:

a bistable conduction circuit responsive to said lock pulse to generate a step-function pulse; and

a one-shot multivibrator connected to said bistable conduction circuit and responsive to said step-function pulse to generate and apply a square-wave pulse of a given duration to said gate means.

8. An electronic lock and key system comprising:

key pulse generating means for generating a pulseduration coded pulse in response to an operating potential applied thereto;

lock pulse generating means for generating a lock pulse having a pulse duration at least equal to said coded pulse, in response to an operating potential applied thereto;

pulse comparison means for generating a control pulse in response to synchronism between said coded pulse and said lock pulse;

a source of operating potential;

means for selectively connecting said source of operating potential to said key pulse generating means and said lock pulse generating means;

means connected to said comparison means and responsive to said control pulse;

said key pulse generator means comprising:

a portable key member adapted to engage said selective connecting means;

a transistorized pulse-duration code generator carried by said key member; and

circuit connector means carried by said key member for connecting said code generator to said selective connecting means.

9. An electronic lock and key system comprising:

key pulse generating means for generating a pulseduration coded pulse in response to an operating potential applied thereto;

lock pulse generating means for generating a lock pulse having a pulse duration at least equal to said coded pulse, in response to an operating potential applied thereto;

pulse comparison means for generating a control pulse in response to synchronism between said coded pulse and said lock pulse;

a source of operating potential;

means for selectively connecting said source of operating potential to said key pulse generating means and said lock pulse generating means;

means connected to said comparison means and responsive to said control pulse; and

means responsive to said coded pulse for limiting the transmission of pulses to said comparison means t0 a single coded pulse each time said selective connecting means connects said source of operating potential to said key pulse generating means.

10. An electronic lock and key system comprising:

key pulse generating means for generating a pulseduration coded pulse in response to an operating potential applied thereto;

lock pulse generating means for generating a lock pulse having a pulse duration at least equal to said coded pulse, in response to an operating potential applied thereto;

pulse comparison means for generating a control pulse in response to synchronism between said coded pulse and said lock pulse;

a source of operating potential;

means for selectively connecting said source of operating potential to said key pulse generating means and said lock pulse generating means;

means connected to said comparison means and responsive to said control pulse;

a second key pulse generating means for generating a second pulse-duration coded pulse in response to said control pulse;

a second lock pulse generating means for generating a second lock pulse having a pulse duration at least equal to said second coded pulse, in response to an operating potential applied thereto;

second pulse comparison means for generating an output pulse in response to synchronism between said second coded pulse and said second lock pulse;

means for selectively connecting said source of operating potential to said second key pulse generating means and said second lock generating means; and

an electric latch connected to said second pulse comparison means and operative in response to said output pulse.

References Cited UNITED STATES PATENTS 2,931,916 4/1960 Sinn 340-149 XR 3,134,254 5/ 1964 Richard 70-277 3,142,166 7/1964 Adam et al. 70--282 XR 3,144,761 8/1964 Lee 70--277 RICHARD E. MOORE, Primary Examiner.

MARVIN A. CHAMPION, Examiner.

R. L. WOLFE, Assistant Examiner. 

